Multiple beam laser system for forming stents

ABSTRACT

A system and method for precision cutting using multiple laser beams is described, The system and method includes a combination of optical components that split the output of a single laser into multiple beams, with the power, polarization status and spot size of each split beam being individually controllable, while providing a circularly polarized beam at the surface of a work piece to be cut by the laser beam. A system and method for tracking manufacture of individual stents is also provided.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application No.61/149,621 filed Feb. 3, 2009 and U.S. Provisional Application No.61/149,645 filed Feb. 3, 2009, incorporated by reference in theirentireties.

This application is also related to U.S. application Ser. No. ______entitled IMPROVED LASER CUTTING PROCESS FOR FORMING STENTS, filed Feb.3, 2010, and U.S. application Ser. No. ______ entitled IMPROVED LASERCUTTING SYSTEM, filed Feb. 3, 2010.

BACKGROUND

1. Field of the Invention

The present invention relates generally to implantable medical devicesand to a method for manufacturing implantable medical devices. Theseimplantable medical devices may also be capable of retaining therapeuticmaterials and dispensing the therapeutic materials to a desired locationof a patient's body. More particularly, the present invention relates toa method for forming the structure of a stent or intravascular orintraductal medical device.

2. General Background and State of the Art

In a typical percutaneous transluminal coronary angioplasty (PTCA) forcompressing lesion plaque against the artery wall to dilate the arterylumen, a guiding catheter is percutaneously introduced into thecardiovascular system of a patient through the brachial or femoralarteries and advanced through the vasculature until the distal end is inthe ostium. A dilatation catheter having a balloon on the distal end isintroduced through the catheter. The catheter is first advanced into thepatient's coronary vasculature until the dilatation balloon is properlypositioned across the lesion.

Once in position across the lesion, a flexible, expandable, preformedballoon is inflated to a predetermined size at relatively high pressuresto radially compress the atherosclerotic plaque of the lesion againstthe inside of the artery wall and thereby dilate the lumen of theartery. The balloon is then deflated to a small profile, so that thedilatation catheter can be withdrawn from the patient's vasculature andblood flow resumed through the dilated artery. While this procedure istypical, it is not the only method used in angioplasty.

In angioplasty procedures of the kind referenced above, restenosis ofthe artery often develops which may require another angioplastyprocedure, a surgical bypass operation, or some method of repairing orstrengthening the area. To reduce the likelihood of the development ofrestenosis and strengthen the area, a physician can implant anintravascular prosthesis, typically called a stent, for maintainingvascular patency. In general, stents are small, cylindrical deviceswhose structure serves to create or maintain an unobstructed openingwithin a lumen. The stents are typically made of, for example, stainlesssteel, nitinol, or other materials and are delivered to the target sitevia a balloon catheter. Although the stents are effective in opening thestenotic lumen, the foreign material and structure of the stentsthemselves may exacerbate the occurrence of restenosis or thrombosis.

A variety of devices are known in the art for use as stents, includingexpandable tubular members, in a variety of patterns, that are able tobe crimped onto a balloon catheter, and expanded after being positionedintraluminally on the balloon catheter, and that retain their expandedform. Typically, the stent is loaded and crimped onto the balloonportion of the catheter, and advanced to a location inside the artery atthe lesion. The stent is then expanded to a larger diameter, by theballoon portion of the catheter, to implant the stent in the artery atthe lesion. Typical stents and stent delivery systems are more fullydisclosed in U.S. Pat. No. 5,514,154 (Lau et al.), U.S. Pat. No.5,507,768 (Lau et al.), and U.S. Pat. No. 5,569,295 (Lam et al.).

Stents are commonly designed for long-term implantation within the bodylumen. Some stents are designed for non-permanent implantation withinthe body lumen. By way of example, several stent devices and methods canbe found in commonly assigned and common owned U.S. Pat. No. 5,002,560(Machold et al.), U.S. Pat. No. 5,180,368 (Garrison), and U.S. Pat. No.5,263,963 (Garrison et al.).

Intravascular or intraductal implantation of a stent generally involvesadvancing the stent on a balloon catheter or a similar device to thedesignated vessel/duct site, properly positioning the stent at thevessel/duct site, and deploying the stent by inflating the balloon whichthen expands the stent radially against the wall of the vessel/duct.Proper positioning of the stent requires precise placement of the stentat the vessel/duct site to be treated. Visualizing the position andexpansion of the stent within a vessel/duct area is usually done using afluoroscopic or x-ray imaging system.

Although PTCA and related procedures aid in alleviating intraluminalconstrictions, such constrictions or blockages reoccur in many cases.The cause of these recurring obstructions, termed restenosis, is due tothe body's immune system responding to the trauma of the surgicalprocedure. As a result, the PTCA procedure may need to be repeated torepair the damaged lumen.

In addition to providing physical support to passageways, stents arealso used to carry therapeutic substances for local delivery of thesubstances to the damaged vasculature. For example, anticoagulants,antiplatelets, and cytostatic agents are substances commonly deliveredfrom stents and are used to prevent thrombosis of the coronary lumen, toinhibit development of restenosis, and to reduce post-angioplastyproliferation of the vascular tissue, respectively. The therapeuticsubstances are typically either impregnated into the stent or carried ina polymer that coats the stent. The therapeutic substances are releasedfrom the stent or polymer once it has been implanted in the vessel.

In the past, stents have been manufactured in a variety of manners,including cutting a pattern into a tube that is then finished to formthe stent. The pattern can be cut into the tube using various methodsknown in the art, including using a laser.

Laser cutting of the stent pattern initially utilized lasers such as theNd:YAG laser, configured either at its fundamental mode and frequency,or where the frequency of the laser light was doubled, tripled, or evenquadrupled to give a light beam having a desired characteristic toensure faster and cleaner cuts.

Recently, lasers other than conventional Nd:YAG lasers have been used,such as diode-pumped solid-state lasers that operate in the short pulsepico-second and femto-second domains. These lasers provide improvedcutting accuracy, but cut more slowly than conventional lasers such asthe long pulse Nd:YAG laser. One approach to improving the efficiency ofthe pico-second and femto-second lasers has been to configure them sothat the light from a single laser is split into multiple beams so thatmultiple stent with the same pattern, or different patterns, may be cutduring a single cutting cycle. Such systems, however, must employcomplex optical systems that, if not properly aligned, may reduce thecutting efficiency of the laser.

Present multiple beam laser systems typically include a quarter-waveplate through which a linear polarized laser beam is directed to producea circular polarized beam. This circular polarized beam is thenredirected through a high reflection mirror and a focusing lens to thework piece. The high-reflection mirror typically has high reflection forboth s and p polarized beams. However, the phases for s and p polarizedbeams are not controlled. Therefore, after reflection, the s and ppolarized beams will be reflected with different phase changes for eachbeam. Even with slightly different reflections, since the coating on themirrors are not identical, resulting in slightly different reflectivityof the s and p beams, the circular polarized beam will becomeelliptically polarized because of the different phase changes. Suchelliptically polarized laser beams have been found to be less efficientat cutting multi-directional patterns, such as are cut into stents.

This problem is further aggravated by polarization shifts induced whenthe laser beam travels through beam splitting mirrors. The polarizationof one split beam may be significantly different from another splitbeam. As a result, tuning of the cutting laser beam is difficult becauseadjustment of one cutting laser beam polarization to an ideal state willnecessarily adjust another laser beam to non-ideal state.

What has been needed, and heretofore unavailable, is an efficient andcost-effective multi-beam laser cutting system that is capable of beingaligned so that the power level and spot size of each cutting beam canbe individually controlled. Further, the system should also ensure thatthe light of each cutting beam delivered to the work piece is circularlypolarized to optimize cutting quality and speed. Use of such a systemwill provide enhanced throughput, and may also include enhancements fortracking the manufacturing history of individual stents. The presentinvention satisfies these, and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to an optical design for a multiplebeam laser system. The various aspects of the present invention are animprovement over previously developed multiple beam laser systemsbecause circular polarization is introduced to the laser beam after thebeam reflects from the last mirror in the optical path. As a result, thecutting laser beam is maximally circular rather than elliptical orlinear, which improves the cutting quality and efficiency for amulti-directional cutting pattern, such as is cut into a stent.

In another aspect, the invention also incorporates high-reflectionmirrors and beam splitting mirrors with zero phase shifts in order tomaintain the beam integrity and to ensure maximum circular polarizationof the cutting laser beam.

In yet another aspect, the invention incorporates a quarter wave platepositioned downstream of all reflecting mirrors and beam splittingelements to maintain beam integrity and ensure maximum circularpolarization of the laser beam.

In still another aspect, power level, polarization status and spot sizeof each of the independent lasers beams of the multiple beam lasersystem can be controlled, resulting in improvements in the efficiencyand economy which allows for scaled up manufacturing ofprecision-machined parts, such as stents. Moreover, tuning of each laserbeam to provide a maximally circularized polarized light beam at thework part ensures an efficient and high-quality laser cut.

In a further aspect, the inventions comprises a multiple beam lasersystem, including a laser capable of emitting a linearly polarized laserbeam, at least one partially transmissive and partially reflectivemirror capable of transmitting and reflecting the linearly polarizedlaser beam, the partially transmissive and partially reflective mirrorbeing used to divide a single laser beam into two laser beams, a halfwave plate, the half wave plate being capable of being rotated to alterthe polarization direction of the incoming laser beam, a polarizer,which, along with the half wave plate provides an attenuation featurefor adjusting the power level of the laser beam, an adjustable beamexpander for adjusting the spot size and also for compensating for otheroptical defects caused by variation of the raw laser beam size or in theperformance of other optical elements in the optical path, aquarter-wave plate positioned after all other mirrors and beam splittersin the optical path, and for introducing circular polarization into thelaser beam and a focal lens for focusing the laser beam on a work piece.

In a further aspect, the invention provides a method of manufacturingstents using an automated process that allows for batching of stents asrequired. The automation process includes packaging, identification, andmarking systems that permit material control and lot history to bemaintained for effective traceability. Finished stents produced by thisprocess can be delivered as input material for manufacturing a stentdelivery system. Since the process is automated and permits some degreeof action, it is possible to run the process at full capacitycontinuously, thereby fully utilizing the laser systems and minimizingcosts associated with laser downtime.

In another aspect, the system and method of the present inventionprovides an automated system for manufacturing stents utilizing, amongother processes and equipment, multiple laser beams formed from a singlelaser source.

In yet another aspect, the present invention includes using a laser tocut an identification tag from a tube as part of a stent pattern beingcut to form a stent. The tag includes information related to themanufacturing history of the stent.

In still another aspect, the present invention includes a multiple beamlaser system, comprising: a laser capable of emitting a linearlypolarized laser beam; at least one partially transmissive and partiallyreflective beam splitter capable of transmitting and reflecting thelaser beam at a nearly linear polarization and which introduces nopolarization change to the laser beam and which is capable of dividingthe laser beam emitted by the laser into two laser beams; a half waveplate disposed in an optical path of a selected one of the laser beams,the half wave plate being capable of being rotated to alter thepolarization direction the laser beam; a polarizer disposed in theoptical path of the selected laser beam for adjusting the laser power ofthe selected laser beam at a selected polarization direction; anadjustable beam expander disposed in the optical path of the selectedlaser beam to adjust the size of the selected laser beam; a quarter-waveplate disposed in the selected beam after the beam splitter forintroducing circular polarization into the selected laser beam; and afocusing lens for focusing the selected laser beam to a desired spotsize.

In another aspect, the beam expander is disposed in the optical pathdownstream of the polarizer. In yet another aspect, the beam expander isdisposed in the optical path upstream of the polarizer. In still anotheraspect, the half wave plate is disposed upstream of the polarizer. Instill another aspect, the quarter wave plate is disposed downstream ofthe polarizer.

In an even further aspect, a second polarizer is disposed in the opticalpath of a second selected one of the laser beams; and a second beamexpander is disposed in the optical path of the second selected one ofthe laser beams upstream from the second polarizer. In another aspect,the polarizer is disposed in the between the laser and the at least onepartially transmissive and partially reflective mirror.

In still another aspect, a power meter is disposed in the optical pathof the laser beam to measure the power of the laser beam.

In yet another aspect, the invention includes an achromatic lens; acamera configured to view the cutting process through the achromaticlens; and a dichroic mirror for reflecting the selected laser beam andfor providing an optical pathway allowing the camera to view the cuttingprocess. In another aspect, the dichroic mirror is a long wave passmirror.

In a further aspect, the invention also includes a system foridentifying a stent, comprising: a laser for providing a laser beam; acomputer controlled locating fixture for moving a tube in a selectedmanner beneath the laser beam to cut a pattern into the tube, thepattern representing information related to the identification of astent to be cut from the tube.

In another aspect, the pattern includes a tag upon which information isetched by the laser beam, and in still another aspect, the pattern is abar code.

In a still further aspect, the invention includes a method formanufacturing stents using a multiple beam cutting process comprising:splitting a laser beam into at least two laser beams; cutting a stentpattern into a tube using one of the at least two laser beams; markingthe stent pattern with an identifier; sorting a batch of stents intoindividual stents; reading the identifier on an individual stent;marking information related to the identifier on a vial; and placing theindividual stent into the marked vial.

In a further aspect, the invention also includes removing remove theidentifier from the stent. In still another aspect, removing theidentifier includes electrochemically polishing the stent to remove theidentifier, and in still another aspect, removing the identifierincludes cutting the identifier from the stent.

In yet another aspect, reading the identifier on the stent includes:digitizing the identifier; and storing the digitized identifier in amemory in operable communication with a processor. In still anotheraspect, marking information related to the identifier on a vialincludes: reading the digitized identifier of a stent from the memory;associating the digitized identifier with data related to themanufacture of the stent; marking selected data related to themanufacture of the stent on the vial.

Other features and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial view of a stent showing various elements of thestent pattern.

FIG. 1A is a cross-sectional view of a portion of one of the elements ofthe stent pattern.

FIG. 2 is a side view of a typical arrangement of a computer controlledcutting system using a laser beam to cut stent patterns into tubing toform a stent.

FIG. 3 is a schematic design of an embodiment of an optical layout for amultiple beam laser system in accordance with principles of the presentinvention.

FIG. 4 is a schematic design of an embodiment of an optical layout for amultiple beam laser system which typically produces ellipticallypolarized beams which cannot be individually controlled.

FIG. 5 is a schematic design of yet another embodiment of an opticallayout for a multiple beam laser system in accordance with theprinciples of the present invention. An online vision system havingon-axis or off-axis illumination is also illustrated.

FIG. 6 is an alternative embodiment of the optical layout of FIG. 5showing placement of the wave plates and polarizer downstream of thebeam expander.

FIG. 7 is another alternative embodiment of the optical layout of FIG. 5showing the beam expander placed in the optical path after the laserbeam has been split once.

FIG. 8 is a schematic design of an alternative embodiment of the opticallayout of FIG. 6 wherein a beam expander is inserted into the opticalpath before the light beam from the laser has been split.

FIG. 9A is a schematic design of an alternative embodiment of theoptical layout of FIG. 8 showing the insertion of an optical elementsuch as an anamorphic prism pairs after the beam expander in order tocorrect beam circularity and/or astigmatism in the laser beam caused bythe laser.

FIG. 9B is a schematic design of an alternative embodiment of theoptical layout of FIG. 8 depicting the insertion of anamorphic prismpairs within each individual laser beams to correct astigmatism causedby both the laser and the optical elements in the optical path.

FIG. 10 is a schematic layout of one embodiment of an automated stentmanufacturing process utilizing multiple cutting beams from a singlelaser source.

FIG. 11 is a top plan view of an embodiment of a marking tag cut by alaser as part of a stent pattern cut from a tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is an enlarged perspective view of a stent 10 illustrating anexemplary stent pattern and showing the placement of interconnectingelements 15 between adjacent radially expandable cylindrical elements.Each pair of the interconnecting elements 15 on one side of acylindrical element are preferably placed to achieve maximum flexibilityfor a stent. In the embodiment shown in FIG. 1, the stent 10 has threeinterconnecting elements 15 between adjacent radially expandablecylindrical elements which are 120 degrees apart. Each pair ofinterconnecting elements 15 on one side of a cylindrical element areoffset radially 60 degrees from the pair on the other side of thecylindrical element. The alternation of the interconnecting elementsresults in a stent which is longitudinally flexible in essentially alldirections. Various configurations for the placement of interconnectingelements are possible. However, as previously mentioned, all of theinterconnecting elements of an individual stent should be secured toeither the peaks or valleys of the undulating structural elements inorder to prevent shortening of the stent during the expansion thereof.

The number of undulations may also be varied to accommodate placement ofinterconnecting elements 15, for example, at the peaks of theundulations or along the sides of the undulations as shown in FIG. 1.

As best observed in FIG. 1, cylindrical elements in this exemplaryembodiment are shown in the form of a serpentine pattern. As previouslymentioned, each cylindrical element is connected by interconnectingelements 15. The serpentine pattern is made up of a plurality ofU-shaped members 20, W-shaped members 25, and Y-shaped members 30, eachhaving a different radius so that expansion forces are more evenlydistributed over the various members.

The afore-described illustrative stent 10 and similar stent structurescan be made in many ways. However, the preferred method of making thestent is to cut a thin-walled tubular member, such as, for example,stainless steel tubing to remove portions of the tubing in the desiredpattern for the stent, leaving relatively untouched the portions of themetallic tubing which are to form the stent. In accordance with theinvention, it is preferred to cut the tubing in the desired pattern bymeans of a machine-controlled laser, as exemplified schematically inFIG. 2.

The tubing may be made of suitable biocompatible material such as, forexample, stainless steel. The stainless steel tube may be Alloy type:316L SS, Special Chemistry per ASTM F138-92 or ASTM F139-92 grade 2.Special Chemistry of type 316L per ASTM F138-92 or ASTM F139-92Stainless Steel for Surgical Implants. Other biomaterials may also beused, such as various biocompatible polymers, co-polymers or suitablemetals, alloys or composites that are capable of being cut by a laser.

Another example of materials that can be used for forming stents isdisclosed within U.S. application Ser. No. 12/070,646, the subjectmatter of which is intended to be incorporated herein in its entirety,which application discloses a high strength, low modulus metal alloycomprising the following elements: (a) between about 0.1 and 70 weightpercent Niobium, (b) between about 0.1 and 30 weight percent in total ofat least one element selected from the group consisting of Tungsten,Zirconium and Molybdenum, (c) up to 5 weight percent in total of atleast one element selected from the group consisting of Hathium, Rheniumand Lanthanides, in particular Cerium, (d) and a balance of Tantalum

The alloy provides for a uniform beta structure, which is uniform andcorrosion resistant, and has the ability for conversion oxidation ornitridization surface hardening of a medical implant or device formedfrom the alloy. The tungsten content of such an alloy is preferablybetween 0.1 and 15 weight percent, the zirconium content is preferablybetween 0.1 and 10 weight percent, The molybdenum content is preferablybetween 0.1 and 20 weight percent and the niobium content is preferablybetween 5 and 25 weight percent.

The stent diameter is very small, so the tubing from which it is mademust necessarily also have a small diameter. Typically the stent has anouter diameter on the order of about 0.06 inch in the unexpandedcondition, the same outer diameter of the tubing from which it is made,and can be expanded to an outer diameter of 0.1 inch or more. The wallthickness of the tubing is about 0.003 inch or less.

Referring now to FIG. 2, the tubing 50 is put in a rotatable colletfixture 55 of a machine-controlled apparatus 60 for positioning thetubing 50 relative to a laser 65. According to machine-encodedinstructions, the tubing 50 is rotated and moved longitudinally relativeto the laser 65 which is also machine-controlled. The laser selectivelyremoves the material from the tubing and a pattern is cut into the tube.The tube is therefore cut into the discrete pattern of the finishedstent.

The process of cutting a pattern for the stent into the tubing isautomated except for loading and unloading the length of tubing.Referring again to FIG. 2, it may be done, for example, using aCNC-opposing collet fixture 55 for axial rotation of the length oftubing, in conjunction with a CNC X/Y table 70 to move the length oftubing axially relatively to a machine-controlled laser as described.Alternatively, the collet fixture may hold the tubing at only one end,leaving the opposite end of the tubing unsupported. The entire spacebetween collets can be patterned using the laser. The program forcontrol of the apparatus is dependent on the particular configurationused and the pattern to be cut by the laser.

Referring now to FIG. 3, there is illustrated an exemplary embodiment ofa multiple beam laser system incorporating various aspects of thepresent invention. The advantage of using a multiple bam laser system isthat it splits the beam of a single laser source and directs the splitbeams toward individual working parts to cut stent patterns into theworking parts. Using such a system results in improved throughputbecause multiple laser beams allow multiple stent patterns to be cut inthe same time as a single stent pattern may be cut using a single laserbeam apparatus, thus maximizing the use of an expensive laser having arelatively slow cutting speed, such as a pico-second or femto-secondlaser.

In prior art systems, a linearly polarized laser beam is directedthrough a quarter-wave plate to produce a circular polarized beam. Thiscircular polarized beam is then redirected through a high reflectionmirror and a focusing lens to the work piece. The normal high reflectionmirror has high reflection for the both the s and p beam components.However, in prior art systems, the phases of the s and p beams are notcontrolled. Thus, the circularly polarized beam becomes ellipticallypolarized because of the phase changes. In addition, the coating onvarious optical elements in the system may be imperfect, resulting inslightly different reflectivity for the s and p beam components. Laserbeams with elliptical polarization have been found to be less efficientat cutting multi-directional stent patters, and are undesirable.

This problem of polarization change is aggravated by the beam splittingmirrors in the multiple beam system because the polarization of onesplit beam may be significantly different from another split beam. As aresult, tuning of the cutting laser beam is difficult because adjustmentof one cutting laser beam polarization to an ideal state willnecessarily adjust another beam to a non-ideal state.

FIG. 3 shows a multiple laser beam system 100 having a laser source 105.Laser source 105 may be a short-pulse, high-intensity laser such as apico-second laser. Those skilled in the art will appreciate that otherlaser sources may be used without departing from the scope of theinvention, including, but not limited to, gas laser such as carbondioxide, carbon monoxide, solid-state lasers such as Nd:YAG, ytterbiumor any other laser capable of producing a beam that can cut a stentpattern.

Laser 105 produces an s polarized laser beam 110 that is directed at abeam splitter 115 that is partially transmissive and partiallyreflective, which transmits and reflects the beam at linearpolarization. The transmitted beam and the reflected beam remain inlinear polarization even if the beam splitter 115 has slightly differentrefectivity/transmissivity and a different phase shift.

The linearly polarized laser beam may then be split by partialtransmitting/reflecting beam splitter 125, resulting in multiplepotential cutting beams. Once again, in this arrangement, the beamsplitter 125 does not change the linear polarization of the beam even ifthe beam splitter has slightly different refectivity/transmissivity anda different phase shift. These beams may be directed to additionalpartial transmitting/reflecting mirrors as necessary either immediatelyor after modification by other optical components, to split the beamsinto further cutting beams.

Once an independent cutting laser beam is formed in this manner, it willinteract with a number of optical components to produce an idealizedcutting laser beam with desired power, spot size, and polarizationcharacteristics. As will be discussed in more detail below, thesecharacteristics can be individually controlled.

The power of the laser beam is controlled using a combination of a halfwavelength plate 130 and a polarizer 135. Half wave plate 130 can berotated as needed to change the polarization direction of the incominglinearly polarized laser beam. As the modified laser beam exits the halfwave plate 130 and travels through the polarizer 135, polarizer 135filter the light based on the match between the incoming laserpolarization and the polarizer construction. By rotating the half-waveplate 130, the laser beam output of the polarizer can vary between amaximum when the incoming light polarization matches ideally with thepolarizer orientation and a minimum when the incoming light polarizationis perpendicular to the polarizer orientation. The output of polarizer135 determines the power of the cutting laser beam. The half wave plate130 and polarizer 135 also maintain the linear polarization of the laserbeam as it travels towards the working part, which is important to allowfor optimal circular polarization of the laser beam at the cuttingsurface.

At any point after laser beam 110 exits polarizer 135, it may be passedthrough an adjustable beam expander 140 that is capable of modifying thespot size of the laser beam without modifying the polarization of thelaser beam. It will be appreciated that various layout of the opticalcomponents of the laser system depicted in FIG. 3 are possible, such aspositioning the adjustable beam expander 140 closer to the working part.Due to space requirements of the adjustable beam expander 140, however,a more compact system may be achieved, if necessary, by positioning theadjustable beam expander as shown in FIG. 3. One example of anadjustable beam expander that is suitable for use in the describedsystem is the model EPZ-13C-THG for 355 nm laser light made byBeamExpander.com LLC.

The laser beam may be reflected by one or more highly reflective mirrors145. In a preferred embodiment, these mirrors have a high reflectivityfor the laser beam, that is, greater than 99%. Mirrors 145 also maintainthe linear polarization of the laser beam 110 as it travels toward theworking part 160. In another embodiment, mirror 145 may be replaced byan optical element having a coating which allows for a high reflectionfor the laser cutting beam, and high transmission for the anillumination light to provide for lighting of the work piece so it canbe view by an on-line camera or other viewing device.

Prior to reaching working part 160, but after reflecting from the lastmirror 145 in the optical path, the laser beam 110 passes through aquarter wave plate 150 that introduces circular polarization into thelaser beam 110. Maintenance of linearity polarization in the laser beamuntil it passes through quarter wave plate 150 is important in thatelliptical polarization of the laser beam may result otherwise. Circularpolarization of the laser beam 110 when it impinges on the material tobe cut results in a more efficient and higher quality cut of the workingpart.

Depending on the overall design requirements of the laser cuttingstations, the beam may pass through lenses 155 or other polarizationinsensitive optical components after the beam has passed through thequarter wave plate 150 as long as the polarization of the laser beam isnot modified.

While the components of only two of the beam arms have been identifiedwith reference numerals in FIG. 3, it will be appreciated that theadditional two beam arms of FIG. 3 may be identical to the numbered beamarms. Alternatively, the additional beam arms may include more or lessoptical components as required by the design needs of the cuttingstations, so long as the polarization of the resultant laser beam at thework surface is ideally circularly polarized.

It will be appreciated by those skilled in the art that the opticaldesign of the laser cutting system depicted in FIG. 3 produces multiplelaser beams, with each laser beam being individually controllable withrespect to power level, polarization status, and spot-sizedcharacteristics. For example, polarization of the laser beam iscontrolled by polarizer 135 and quarter wave plate 150 and power levelis controlled by polarizer 135 and half wave plate 130. Spot size iscontrolled using a combination of adjustable beam expander 140 andfocusing lenses 155. In an alternative embodiment, an extra modulatorand switch may be used to control the repetition rate, power level andon/off control of each individual laser beam.

FIG. 4 is a schematic of an optical layout which is capable of producingcircularly polarized beams. In this layout, however, the two beamscannot be individually controlled. In this embodiment, laser light isproduced by a linearly p[polarized laser 205 which is directed through ahalf wave plate 215, through a polarizer 220, then through a quarterwave plate 230 to generate a circularly polarized beam. The circularlypolarized laser beam then passes through an adjustable beam expander225, which is used to control the ultimate spot size of the beam. Thecircularly polarized beam impinges upon partial beam splitter 235, wherea portion of the beam is reflected downwards through a focusing lens 240to cut a stent pattern into a work piece 250. A portion of the laserbeam is also transmitted through beam splitter 235 to a long wave passdichroic mirror 237, where the laser beam is reflected downwards througha focusing lens 240 to cut a stent pattern into a second work piece 250.A protection window 245 may be disposed between the focusing lens 240and the work piece 250 to prevent contamination of the optical systemfrom debris generated during the cutting process.

Returning again to beam splitter 235, an illumination light and a viewof the laser beam falling upon the work piece may also be transmittedupwards through an achromatic lens 255 to fall upon a charge coupledevice 260. This assembly allows for beam alignment on the work pieceand monitoring cutting status. Similarly, an illumination light and aview of the cutting beam on the work piece may be transmitted upwardsthrough an achromatic lens 255 to fall upon a second charge coupledevice 260. It should be noted that because the polarizer 220 and beamexpander 225 are located prior to the beam-splitting mirror 235, thebeams cannot be individually controlled, which may result in the twolaser beams having different power levels and spot sizes. This may alsobe disadvantageous if any elliptical polarization is introduced to laserbeam by mirror 235 or mirror 237, which can occur since the oncecircularly polarized beam passes through the beam splitter 235 andmirror 237 which may introduce different reflectivity/transmissivity andphase shift to the s and p beam components.

FIG. 5 depicts another embodiment of an optical layout similar to theoptical layout set forth with regard to FIG. 3. In FIG. 5 charge coupledevices and achromatic lenses have been added to allow for monitoring ofthe individual laser cutting status.

In the embodiment illustrated in FIG. 5, a laser 305 produces a linearlypolarized laser beam 310 that is directed at a mirror high reflectionmirror 312 maintains the linear polarization of the laser beam. Linearlypolarized laser beam 310 is then directed at beam splitter 315 that ispartially transmissive and partially reflective, which transmits andreflects the beam at linear polarization. The transmitted beam and thereflected beam remain in linear polarization even if the beam splitterhas slightly different refectivity/transmissivity and a different phaseshift.

The transmitted portion of laser beam 310 in this embodiment may then beredirected by reflective mirror 320, which also keeps the reflected beamlinearly polarized. The portion of the laser beam reflected by mirror315 may, as illustrated, provide a laser source for at least one otherlaser optical train that may be used to cut yet another work piece.

After being reflected by mirror 320, the laser beam 310 may then besplit by partial transmitting/reflecting mirror 325, resulting in twocutting beams. These beams may be directed to additional partialtransmitting/reflecting mirrors as necessary either immediately or aftermodification by other optical components, to split the beams intofurther cutting beams.

Once an independent cutting laser beam is formed in the manner describedabove, it will interact with a number of optical components to producean idealized cutting laser beam with desired power, spot size, andpolarization characteristics which can be individually controlled

Similar to the laser system described above with reference to FIG. 3,the power of each individual laser beam is controlled using acombination of a half wavelength plate 330 and a polarizer 335. Halfwave plate 330 can be rotated as needed to change the polarizationdirection of the incoming laser beam. As the modified laser beam exitsthe half wave plate 330 and travels through the polarizer 335, polarizer335 filters the light based on the match between the incoming laserpolarization and the polarizer construction. By rotating the half-waveplate 330, the laser beam output of the polarizer can vary between amaximum when the incoming light polarization matches ideally with thepolarizer orientation, and a minimum when the incoming lightpolarization is perpendicular to the polarizer orientation. The outputof polarizer 335 determines the power of the cutting laser beam. Thehalf wave plate 330 and polarizer 335 also maintain the linearpolarization of the laser beam as it travels towards the working part,which is important to allow for optimal circular polarization of thelaser beam at the cutting surface.

At any point after laser beam 310 exits polarizer 335, it may be passedthrough an adjustable beam expander 340 that is capable of modifying thespot size of the laser beam without modifying the polarization of thelaser beam.

The laser beam may be reflected by one or more highly reflective mirrors345. In a preferred embodiment, these mirrors have a high reflectivityand include a coating that provides no power reduction of the laser beamas it is reflected and transmit the illuminated light so that thefocused cutting spot of the laser beam cutting the work piece can beimaged onto the charge coupled device. Mirrors 345 also maintain thelinear polarization of the laser beam 310 as it travels toward the workpiece 360.

Prior to reaching work piece 360, but after reflecting from the lastmirror 345 in the optical path, the linearly polarized laser beam 310passes through a quarter wave plate 350 that introduces circularpolarization into the laser beam 310.

Depending on the overall design requirements of the laser cuttingstations, the beam may pass through lenses 355 or other polarizationinsensitive optical components after the beam has passed through thequarter wave plate 350 as long as the polarization of the laser beam isnot modified.

While the components of only two of the beam arms have been identifiedwith reference numerals in FIG. 5, it will be appreciated that theadditional two beam arms of FIG. 3 may be identical to the numbered beamarms. Alternatively, the additional beam arms may include more or lessoptical components as required by the design needs of the cuttingstations, so long as the polarization of the resultant laser beam at thework surface is ideally circularly polarized.

Another feature of the system depicted in FIG. 5 is the use of acharge-coupled device 370 and achromatic lens 365 assembly formonitoring laser cutting. Additionally, power meters 375 may be insertedalong the optical path in selected locations to monitor the power oflaser beam 310.

In yet another embodiment, the system may include a mirror 345 in theoptical paths of one, two or more of the individual beams arranged sothat an off-axis light 377 can be used to illuminate the work piece 360so that the cutting status of the stent can be monitored using chargecouple device 370. A focusing lens 380 may also be used to focus theillumination light as required. In another embodiment, an off-axis light385 may be used to illuminate the work piece 360.

FIG. 6 illustrates an alternative embodiment of the system shown in FIG.5 with the exception that the wave plates 430 and polarizer 435 arelocated in the laser beam at a point after the beam has passed throughthe beam expander 440.

In this embodiment, the initial portion of the optical path includinglaser 405, reflecting mirror 412, reflecting/transmitting mirror 415,reflecting mirror 420 and reflecting mirror 425 and reflecting mirror420 are similar to that described with reference to FIG. 5. Theembodiment of FIG. 6 diverges from the embodiment of FIG. 5 after thetwo cutting beams are formed. In this embodiment, laser beam 110 passesthrough beam expander 440 and then is reflected by mirror 445 to passthrough half wave plate 430 and polarizer 450 on its way to work piece460. Note that this arrangement still allows for control of the power,polarization and spot size of each individual cutting beam.

FIG. 7 depicts another embodiment of an optical layout wherein the lightfrom the laser source 505 is split into two beams. Each laser beam thenpasses through a beam expander 540. The split laser beam is then splitagain in each arm to form four laser beams which are then directedthrough half wave plates 530 and polarizers 535 before being focusedonto a work piece. The embodiment of FIG. 7 also shows placement ofonline CCD cameras 570 and achromatic lenses 565, as well as an offlinecamera 580, which may be a charge couple device, and achromatic 585 lensfor viewing the cutting process. The advantage of this embodiment isthat it allows for the use of only two beam expanders, rather than thefour beam expanders required in other embodiments. One disadvantage,however, is that spot size uniformity will not be maintained at the samelevels as the embodiments shown in FIG. 3, 5 or 6 because the spot sizeof each laser beam is not individually adjustable.

FIG. 8 is another embodiment of an optical layout wherein a beamexpander is inserted into the optical path before the laser beam fromthe laser source 605 is split. The advantage of this embodiment is thatit requires only a single beam splitter 640. Of course, the disadvantageis that spot size uniformity will not be maintained at the same levelsas other embodiments because the spot size of each laser beam will notbe individually adjustable. Note, however, that because each beam passesthrough half wave plate 630 and polarizer 635, the polarization of eachbeam is individually adjustable, ensuring that the beam spot iscircularly polarized when it shines upon the work piece.

FIG. 9A depicts another embodiment of an optical layout using anamorphicprism pairs inserted into the optical path directly after the beamexpander to correct circularity, beam shifting and possibly astigmatismcaused by the laser. Occasionally, defects in either the design ofoptical components or their manufacture result in less than optimaloptical performance. Such less than optimal optical performancesometimes results in induced astigmatism in the laser beam. This canalso occur if the optics of the laser source are also not exactlyspherical. One skilled in the art will understand that while thisembodiment uses an anamorphic prism pair, other optical devices orelements, such as a cylinder lens, may also be used.

In this embodiment, laser light from laser source 705 is transmittedthrough beam expander 740. A pair of anamorphic prisms 790 is insertedinto the optical path after the beam expander 740 to correct forastigmatism in the laser beam caused by the laser. One example of aprism pair that may be used is model PS870 made by ThorLabs.

FIG. 9B shows an alternative embodiment of the optical design of FIG. 8wherein circularity, beam splitting and astigmatism that are caused notonly by the laser, but as well imperfections in other optical componentsin the optical path can be corrected by insertion of anamorphic prismpairs 790 into the end of the optical path. This arrangement allows forindividual correction of the astigmatism in each of the arms of thelaser cutting setup.

The various embodiments of the present invention provide a multiple beamlaser system for use in cutting stents and other pieces where precisecontrol of the cutting beam with acceptable power level is required.Such a system also allows efficient use of pico-second lasers orfemto-second lasers which are relatively slow compared to traditionallasers systems that utilize Nd:YAG or fiber lasers. Use of such anoptical system as set forth in FIG. 3 makes the use of pico-secondlasers or femto-second lasers feasible for scaled up manufacturing ofmedical device products. The advantages of such a system are that powerlevel, polarization status and spot size, and even beam astigmatism, ofeach individual laser beam of the multiple beam system can beindividually controlled. The optical design of the laser system of thevarious embodiments described above ensure that an efficient andhigh-quality laser cut is made in the work product.

The embodiments of the present invention are improvements over previousdeveloped multiple beam laser systems in that circular polarization isintroduced to the laser beam after the beam transmits and reflects fromall polarization sensitive optics in the optical path. As a result, thecutting laser beam is maximally circularly polarized rather thanelliptically or linearly polarized, which improves the cutting qualityand efficiency for a multi-directional cutting pattern. In addition,each beam is individually controlled to deliver the desired power leveland spot size.

Referring now to FIG. 10, there is a graphical depiction of anembodiment of an automated manufacturing process for producing stentsthat is designed to cooperate with the multi-beam laser system of FIGS.3 and 5-9B above. It will be immediately understood, however, that thestent manufacturing system set forth in FIG. 10 is equally applicable tolaser cutting systems of 1, 2, 3, or even more beams, and is not limitedto the multiple beam laser system described with regard to FIG. 3 et al.

Step 800 of the automated process of FIG. 10 includes a laser source forproviding a beam of laser light that will be used to cut a stent patterninto a stent tube. This laser source may be a traditional laser such asan Nd:YAG or fiber laser. However, the greatest benefit of the presentinvention maybe realized for pico-second and femto-second lasers thatexhibit significantly longer processing times than traditional lasers.The longer processing times and high cost associated with pico-secondand femto-second lasers make it impractical to operate these lasers atless than full capacity.

As set forth with reference to FIG. 3, the laser beam is split intomultiple beams at step 820 to further improve the efficiency of thelaser cutting process because the pico-second laser cutting speeds arerelatively slow by traditional standards. By splitting the beam, asingle laser source may be utilized to cut multiple stents at the sametime. The importance of this beam splitting process is key, because itimproves overall efficiency while maintaining the integrity and efficacyof the split laser beam.

However, once the laser beams are split, even using the apparatus andsystems described herein with reference to at least FIG. 3, theindividual characteristics of each laser cutting beam may be different,resulting in the potential for slight differences in the efficiency andquality of the stent pattern that is cut using the individual beam.Accordingly, it is desirable to provide traceability information that islinked to each individual beam, rather than to the laser source alone.One embodiment of an identification means is described in more detailbelow.

After the laser beam is split into multiple beams in step 820, it may bedirected toward raw tubing where the laser beam is used to cut a stentpattern into the tubing to produce a stent. Various steps may beinvolved in laser cutting the stent, and are dependent upon the designrequirements of each cutting system and product to be produced.

In one embodiment, for example, multiple pass laser cuts or ablationsmay be used to cut the stent from the tubing. Multiple passes may beused to improve the edge quality of the cut stent and to make beamsplitting viable by ensuring the stent can be fully fabricated with alaser beam that has relatively less power than conventional laser beams.At this point in the process, it is advantageous to produce some sort ofidentification means that will link each stent cut to the individualcharacteristics of the laser beam responsible for the cut. Theidentification mark may include a barcode or some other code or othermachine-readable marker that is related to information about the lasersource, the split laser beam, raw tubing material, and/or stent pattern.The information may also be linked to other processing information suchas a manufacturing time stamp. All of this information may be furtherlinked to other information stored in a computer memory or other media,such as a lot history record. This information may include, for example,the operator name, environmental conditions, and the like. It will beappreciated that the purpose of this identifier is to provide a meansfor tracing the history of stent manufacturing.

After the laser beam has been split into individual beams and focusedcorresponding work pieces (raw tubing), a first pass using the laserbeam to cut at least part way through the tubing to cut a pattern intothe stent is performed at step 822. At this point, the stent may also bemarked with a barcode in step 824, with the stent cutting completed insteps 826 and 828.

Where needed, multiple passes of the laser, such as set forth in steps826 through 838 may also performed to cut entirely through the tubing toform a stent. This process allows for partial cutting through thethickness of the stent tube with each pass of the laser. Alternatively,different portions of a stent pattern may be cut during each pass of aprocess using multiple passes of the laser to cut an entire stentpattern into the tube.

For example, in step 826, at least a portion of the pattern is cut intothe tubing to a depth that is less than the wall thickness of thetubing. At this time, a lot identifier, which may be, for example, a barcode or other character or number, or some combination of both, can becut into the surface of the tube to provide for identification andmanufacturing tracking of the finished stent. In step 826, the tubesurface may be cut in such a manner as to allow for a break link layer,the break link layer for maintaining the structural integrity of thestent while the entire pattern is being cut, and which will ultimatelybe cut away when the stent is finished.

The laser cutting process is repeated, possible for many repetitions, insteps 828-830, until just the wall thickness of the tube is reduced to athickness that may be cut away using one more cutting pass by the laser,as indicated by steps 832-834. Finally, the stent pattern is completedin steps 836-838.

The stents output from each laser beam are placed into a separate batch,as indicated in step 850. It should be understood that since the laserbeams are separate, it is possible for each batch of stents to havestents formed from different raw materials or with different stentpatterns. For example, 15-mm length medium pattern stents may beproduced in Batch #1 of step 850 simultaneously with a 30-mm smallpattern stent in Batch #2 of step 850.

Control over the specific stent pattern and configuration is enabledthrough the individual motion control systems of the individual laserbeams. These systems are separate from the laser source. Alternatively,a single motion control system may be used to control the motion ofmultiple cutting pieces that are being cut by separate laser beams. Insuch an embodiment, multiple cutting pieces will be cut with the samestent pattern to promote the most efficient use of the system. Theidentifiers, such as bar codes, attached to each stent ensure that thestents remain separate as they progress through subsequent processsteps. Alternatively, the lot history information described above couldalso be included on batch packaging.

In step 870, the batches of stents are sorted into individual stents forindividual packaging. Sorting techniques for reducing batches toindividual stents can be designed by one skilled in the art. In oneembodiment, for example, such a sorting technique includes a hoppertable that spreads a batch of stents over an area and empties into afunnel shape or convergent recess that outputs single stents. Batchesmay be manually or automatically conveyed from the laser cutting processto this sorting process. Automated conveyance may be accomplished byequipment that includes a batch container placed under the stents asthey are cut. When the stent is formed, it drops into the batchedcontainer. When a predetermined number of stents have been cut by thelaser and then moved into the batch container, which can be determinedthrough use of either a vision recognition system or weight measurement,the batch container may be conveyed by a belt or linkage system to thebatch sorting mechanism.

Before entering the batch sorting mechanism, it may be desirable to havethe stent undergo an ultrasonic cleaning process. The ultrasoniccleaning process may occur within the batch container, or the batchcontainer may empty into a second specialized ultrasonic cleaning bath.The ultrasonic cleaning bath may subsequently be emptied automaticallyor manually into a sieve or heat drying process to make the stents readyfor sorting. The dried stent batch may then be conveyed to the sortingmechanism for sorting in accordance with step 870.

In one embodiment, in parallel to the batch sorting process 870, a vialfeeding mechanism may be used in step 890 to provide vial containersthat are capable of holding a single stent. This parallel sortingprocess and conveyance of vial containers is important to automation ofthe entire process as it ensures that individual vial containers andindividual stents arrive in the process simultaneously. After the stentshave been individually sorted, they are conveyed to an imaging device atstep 900 that is operated in combination with a computer processor todetect and transfer information provided on the unique identifierattached to each stent to a memory of the computer. Such information mayinclude, for example, as a serial number or barcode as described above.When the information of the unique identifier has been transferred tothe computer, the computer, operating under the control of suitableprogramming commands embodied in software or hardware, performs a writecommand that sends the information to a laser marking system in step 920that is in physical communication with the vial feeding mechanism.

As the vials are individually conveyed in parallel with the individualstents, they pass by the laser marking system and are marked in step 920with the information that is communicated by the computer. For example,as an individual stent is monitored by the imaging device in step 900,the device may detect the unique identifier mark, such as a bar code,and then send a signal to the computer that, in turn, sends a signal tothe laser marking system commanding the laser marking system to mark avial with the same unique identifier. In this manner, a vial having theappropriate identifier information is created and as the stent and vialcome off of their respective conveyors, they are able to be matched instep 940. In this manner, the individual manufacturing history may betraced with reference to the identification information marked onto thevial holding the stent.

In an alternative embodiment, the vial may be marked with a differentidentifier based on a conversion command that is executed in accordancewith software commands stored in the computers memory. For example, thisconverted command may result in an identifier that takes into accountboth the laser cutting lot history information from the originalidentifier and also links the individual stent to information related tothe ultrasonic cleaning and sorting processes. This provides a mechanismfor automatically preparing a lot history record that traces eachmanufacturing step associated with formation of the final stent.

In step 940, the sorted stents and marked vials are matched according tothe identifying information included on the stent and vial. Suchmatching may occur either manually, or may be done by an automatedsystem. Since the conveyance systems for the individual stents andindividual vials may be set up in parallel, they serve as input streamsto the matching equipment. Thus, computer controlled matching machinemay automatically place a stent in each vial. If necessary, a furtheridentification step could be used to read the identifier on the stentand on the laser-marked vial just prior to packaging the stent in thevial to ensure that the proper stent is placed within the proper vial.

After the individual stents are stored within the marked vials, thevials may be conveyed individually or in batches in step 950 accordingto their lot history to an electrochemical polishing step 960. Thepolishing process may be conducted either manually or automatically, andis envisioned as providing for tracing the process applied to eachsingle part. Moreover, this process may also include non-electricallybased polishing processes such as acid etches and passivation steps.

The polishing process may be performed in the same manufacturing line asthe laser cutting and packaging steps, or it may alternatively beperformed in a separate manufacturing line. In any case, stenttraceability is maintained during the polishing process by use of themarked vials.

In one embodiment of the present invention, the unique identifierinformation attached to stent may be removed during the electrochemicalpolishing step 960. This may be accomplished by polishing away themarked label, removing a sufficient depth of material to remove themarking. Alternatively, where the unique identifier is in the shape of atag or other physical device attached to the stent, the polishingprocess may remove the attachment of the tag or device and allowseparation of the tag or device from the stent. After removal of theidentification tag or device or laser marking on the surface of thestent, the marked vial serves as the identification label that allowsthe stent information to trace back to the original laser cuttingprocess.

Following polishing of the stent, the stents are replaced in theirrespective storage vials and are conveyed either individually or inbatches based on the stent size and pattern in step 980. The finishedstents are either stored for further processing or are packaged.

FIG. 11 illustrates one embodiment of an identification tag which isformed on a stent during the laser cutting process, such as in step 824,described above. In this embodiment, a small tab 1000 is included aspart of the stent pattern, such as, for example, attached to a stentstrut 1010. Those skilled in the art will immediately appreciate thatthe tab may be attached to stent in any of a variety of locations, asdetermined by the design of the stent pattern and to promote efficientmanufacture of the stent.

The tab 1000 includes an identification mark 1020, such as a serializednumber or other information, that is cut on the tab, preferably by thelaser-cutting beam, when the stent pattern is cut into the tube. Theidentification mark 1020 may take some form other than a serial number,such as, for example, a barcode or some other machine-readable markerthat is contains or represents information about selected portions ofthe stent manufacturing process, such as, for example, the laser source,the individual laser beam used to cut the stent, raw tubing material,particular stent pattern, electrochemical polishing and the like.

As described above, the information may also be linked to otherprocessing information, such a manufacturing time stamp, or otherinformation stored in a lot history record such as the operator name,environmental conditions, and the like. The tab 1000 of this embodimentmay be removed during a post-processing step, such as after the vial andstent have been matched in step 940, either though a manual process orthrough an automatic process such as an acid etch or the like.

The various embodiments of the automated process described improve theefficiency of the stent manufacturing process by maximizing thethroughput of the laser cutting process while maintaining unit controlwith additional marking and identification techniques. Moreover, sincebatching of stent manufacture is used there is minimal downtimeassociated with product line change-outs and maintenance, since thelasers and electro-polishing processes do not need to be retooled orreprogrammed for each batch of stents. It should be understood that thevarious embodiments of the above-described automated stent cuttingprocess are applicable to the manufacturer of any stent pattern usingany available stent material.

It will be apparent from the foregoing that the present inventionprovides a new and improved method and apparatus for direct lasercutting of metal stents enabling greater precision, reliability,structural integrity and overall quality, minimal creation of heataffected zones (HAZ), without burrs, slag or other imperfections whichmight otherwise hamper stent integrity and performance while providingfor highly efficient use of a laser cutting system. Moreover, variousembodiments of the present invention also provide for tracking themanufacturing history of a cut stent. Other modifications andimprovements may be made without departing from the scope of theinvention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1. A multiple beam laser system, comprising: a laser capable of emittinga linearly polarized laser beam; at least one partially transmissive andpartially reflective beam splitter capable of transmitting andreflecting the laser beam at a nearly linear polarization and whichintroduces no polarization change to the laser beam and which is capableof dividing the laser beam emitted by the laser into two laser beams; ahalf wave plate disposed in an optical path of a selected one of thelaser beams, the half wave plate being capable of being rotated to alterthe polarization direction the laser beam; a polarizer disposed in theoptical path of the selected laser beam for adjusting the laser power ofthe selected laser beam at a selected polarization direction; anadjustable beam expander disposed in the optical path of the selectedlaser beam to adjust the size of the selected laser beam; a quarter-waveplate disposed in the selected beam after the beam splitter forintroducing circular polarization into the selected laser beam; and afocusing lens for focusing the selected laser beam to a desired spotsize.
 2. The system of claim 1, wherein the beam expander is disposed inthe optical path downstream of the polarizer.
 3. The system of claim 1,wherein the beam expander is disposed in the optical path upstream ofthe polarizer.
 4. The system of claim 1, wherein the half wave plate isdisposed upstream of the polarizer.
 5. The system of claim 1, whereinthe quarter wave plate is disposed downstream of the polarizer.
 6. Thesystem of claim 1, further comprising: a second polarizer disposed inthe optical path of a second selected one of the laser beams; and asecond beam expander disposed in the optical path of the second selectedone of the laser beams upstream from the second polarizer.
 7. The systemof claim 1, wherein the polarizer is disposed in the between the laserand the at least one partially transmissive and partially reflectivemirror.
 8. The system of claim 1, wherein a power meter is disposed inthe optical path of the laser beam to measure the power of the laserbeam.
 9. The system of claim 1, further comprising: an achromatic lens;a camera configured to view the cutting process through the achromaticlens; and a dichroic mirror for reflecting the selected laser beam andfor providing an optical pathway allowing the camera to view the cuttingprocess.
 10. The system of claim 9, wherein the dichroic mirror is along wave pass mirror.
 11. A system for identifying a stent, comprising:a laser for providing a laser beam; a computer controlled locatingfixture for moving a tube in a selected manner beneath the laser beam tocut a pattern into the tube, the pattern representing informationrelated to the identification of a stent to be cut from the tube. 12.The system of claim 11, wherein the pattern includes a tag upon whichinformation is etched by the laser beam.
 13. The system of claim 11,wherein the pattern is a bar code.
 14. A method for manufacturing stentsusing a multiple beam cutting process comprising: splitting a laser beaminto at least two laser beams; cutting a stent pattern into a tube usingone of the at least two laser beams; marking the stent pattern with anidentifier; sorting a batch of stents into individual stents; readingthe identifier on an individual stent; marking information related tothe identifier on a vial; and placing the individual stent into themarked vial.
 15. The method of claim 14, further comprising: removingremove the identifier from the stent.
 16. The method of claim 15,wherein removing the identifier includes electrochemically polishing thestent to remove the identifier.
 17. The method of claim 15, whereremoving the identifier includes cutting the identifier from the stent.18. The method of claim 14, wherein reading the identifier on the stentincludes: digitizing the identifier; and storing the digitizedidentifier in a memory in operable communication with a processor. 19.The method of claim 18, wherein marking information related to theidentifier on a vial includes: reading the digitized identifier of astent from the memory; associating the digitized identifier with datarelated to the manufacture of the stent; marking selected data relatedto the manufacture of the stent on the vial.